Soap is a common ingredient of detergent powder compositions. It may be included as a detergent active, a builder or a foam suppresser. It may be added to a slurry which is subsequently spray-dried, or in-situ neutralised from the fatty acid and/or dry-mixed with other particulate ingredients, including composite particles which are themselves the product of a spray-drying process or other granulation process.
To formulate most flexibly, it is more advantageous to dry-mix soap with the rest of the ingredients, without intermediate processing. When supplied as a raw material for incorporating in such compositions, soap is often in the form of a fine dusty powder. As well as being difficult to handle, such powders have a tendency to cause respiratory tract irritation in those working with them. It is known to incorporate extruded or flaked soap “noodles” in detergent compositions, which have a “particle” size much greater than found in the aforementioned dusty powders. However, this is often done purely to create a visual effect, for example when such noodles are deliberately coloured as indictia of certain benefits. The noodle format is also not a very cost-effective means of supplying the soap, especially when formulating dry mixed powders.
Laundry detergent compositions have for many years contained anionic surfactants together with nonionic surfactants.
It is well known that many anionic surfactants form calcium precipitates, that reduces their effectiveness and that may adhere to clothes. Especially much used anionic surfactants like sodium linear alkyl benzene sulphonate (NaLAS), and sodium primary alcohol sulphate (NaPAS). Similarly it is know that soaps are also sensitive to calcium precipitation and that it in fact soap precipitates very strongly. It is therefore common to include builders in laundry formulations.
Common builders are phosphates and zeolites. However, phosphates are not favoured because possible eutrification of waterways. Zeolites are insoluble and might leave residues to clothes.
Mixtures of anionic and non-ionic surfactants are less prone to form calcium precipitates, and these mixtures are applied in many European Countries. However, common nonionic surfactants are more liquid-like and are consequently more difficult to process into solid, non-sticky laundry products.
It has now surprisingly been found that although the soap and the anionics precipitate very strongly on their own, and they also precipitate when the anionic and the soap are combined together. When soaps, anionics and nonionics are used in the specific levels and in the specific format detailed in the invention, for example the addition of the majority of the soap granules to the rest of the detergent ingredients at the post dosing stage as a dry-mix soap granule and in the form of highly concentrated granules, this results in the tendency to precipitate in hard water being lower than for formulations containing only the anionic surfactant, only the soap or the anionic and soap in combination. This advantageously enables the reduction of nonionic and builder requirements in such a composition for the prevention of precipitates.